Sand Horizons Research Articles

Groundwater Exploration using Geoelectric Technique in Oru-Ijebu, South-West Nigeria

Forty Vertical Electrical Soundings (VES) were carried out using Allied Ohmega resistivity meter with schlumberger configuration in parts of Oru-Ijebu to determine the necessary geoelectrical parameters for delineating the aquiferous zones. Four to five distinct geoelectric layers were delineated from the survey area except for VESORU21 which exhibited six geoelectric layers namely the top soil, clayey sand/laterite, clay and granite gneiss. The first layer serves as the topsoil with high variable resistivity ranging from 11.2Ωm (VESORU7) to 153.8Ωm (VESORU25) with their corresponding thickness of 0.9m to 3.8m respectively. The thickness of the entire top soil of the investigated area ranges from 0.4m to 3.8m. The second layer is composed of sand, clay sand, laterite and partly sandy clay. The resistivity of clay/clayey sand overburden varying from 16.2Ωm with a thickness of 8.7m in VESORU17 and 484.3Ωm with a thickness of 3m VESORU6. The highest resistivity exhibited by the second layer is 974 Ωm in VESORU30 while its lowest resistivity is 21.9Ωm in VESORU34. The resistivity of the third layer which stands as a weathered lithology ranges from 17.2Ωm with a thickness of 10.3m at VESORU7 to 233.2Ωm at VESORU23 whose thickness is indeterminate due to current termination in the field to 196 Ωm; typically diagnostic of clay/clayey sand horizon except beneath VESORU1, VESORU2, VESORU11, VESORU30, VESORU32, VESORU34, and VESORU36 where the inferred lithology is sandstone, fresh basement and partly sandy-clay. The fourth and fifth layers are composed of fresh basement formation notably granite-gneiss rocks with resistivity values ranging from 88.5Ωm VESORU20 to 384Ωm in VESORU15. The maximum aquifer thickness is encountered beneath VESORU25. The weathered layer for the study area is thick enough for groundwater accumulation making it a very prolific one. VESORU1, VESORU2 and VESORU23 are marked by a low groundwater yield due to the dip and the thickness.

Reconstructing the Holocene Development of Lake Chaika as an Example of Wetland Formation within the Sand Spit Environment Dynamics: A Case Study from the Curonian Spit, Southeastern Baltic, Russia

The paper provides original data that shed light on the formation dynamics of Lake Chaika, which is situated in the central part of the Curonian Spit and is the only large water body in the sand spits of the southeastern Baltic. Based on the multi-proxy approach, incl. investigation of the lithological structure of the bottom sediment cores, loss-on-ignition analysis, diatom analysis, study of macrofossil remains, and radiocarbon dating, we revealed that Lake Chaika was formed already in historical time, around 200 years ago. Before this period, the lake kettle, presumably, has not submerged during the Littorina transgressions, enabling the terrestrial development of the ecosystems on the moraine protrusion. During the mid-late Holocene (6700–150 cal BP), this depression was occupied by the peat-forming fen and alder carr communities. The peat deposits are separated from the overlying layers of gyttja by the thin sand horizon. We consider it a time marker for the so-called “sand disaster”, which occurred on the territory of the Curonian Spit in the 18th century (≈1700–1800). The change in the hydrological regime of the lake launched the ecosystem shifts during the last two centuries: from the water body to a wetland and vice versa. It is stated eight formation phases of the lake’s ecosystem: the terrestrial development without wet habitats (8900–6700 cal BP), the period of alder carrs (6700–3400 calBP), the sedge fen period (3400–450 cal BP), the period of inundated forest (1500–1700 AD), the “sand disaster” period (1700–1800 AD), the period of eutrophic water body (1800–1900 AD), the period of terrestrialised wetland (1900–1950 AD), and the period of secondary development of eutrophic water body (after 1950 AD).

The effect of clay minerals on in-situ leaching of uranium

In recent years, with the development of techniques and methods for in-situ leaching (ISL), additional uranium extraction from previously worked-out blocks is becoming not only relevant, but also quite achievable. In this case, the extraction of residual uranium reserves from previously worked-out blocks does not require additional costs for the necessary infrastructure. One of the most important factors in the formation of residual uranium reserves in worked-out blocks is the presence of clay minerals in the ore horizon. In this regard, we conducted a number of studies on the adverse and positive effects of clay minerals on ISL process. Water permeability and relatively good filtration (not less than 0.5–1 m/day) of ores and rocks of a productive horizon (aquifer) is the most important hydrogeological factors affecting the performance of uranium ISL. The second most important hydrogeological factor is the lack of fluid communication between the productive aquifer and nonproductive aquifers, i.e., the obligatory presence of aquicludes. The role of clays in these hydrogeological factors is twofold. On the one hand, the presence of clays negatively affects both the solutions filtration rate and uranium extraction. On the other hand, the presence of clay minerals (forming an aquiclude) enhances the effect of ISL. The study findings allowed the role of clay minerals in uranium ISL to be assessed. The diffusion coefficients of nitrate ions in the clays were determined, and the protective effect of aquicludes was calculated. The effect of the clay content in the ore sand horizon on the solutions filtration coefficients was also established. The static uranium exchange capacity of clays was determined by studying the process of uranium sorption by clay samples from sulfate and bicarbonate solutions. The studies established the diffusion coefficients of nitrate ions in montmorillonite and kaolinite clays, which amounted to 3.34 10−6 and 2.14 · 10−6 cm2/s. Taking into account the calculated values of diffusion coefficients, the protective time of the clayey aquiclude for nitrate ions was 43 years. At 20 % clay minerals content, the solution filtration coefficient decreases to values where ISL conditions become unfavorable. It was found experimentally that the sorption of uranium by clay minerals depends on both the nature of the clays and the composition of the solution. Uranium sorption from sulfate solutions proceeds noticeably better than that from bicarbonate solutions. The highest values of the static uranium exchange capacity were obtained for bentonite (104 mg/g).

Geotechnical Considerations for Foundation Design in Parts of Yenagoa, Bayelsa State, Niger Delta Nigeria

This research was to determine geotechnical properties of the subsoils in some part of Yenagoa and environs to obtain proper foundation design parameters, six towns in Yenagoa local government area, Bayelsa state was investigated. Six geotechnical boreholes was drilled and laboratory studies of soils samples were obtained from 0-20.25m deep. Subsurface soil profiles were delineated followed by determination of their index and mechanical properties, including Atterberg limits, particle sizes distribution, undrained shear strength, shear box test and consolidation coefficient. The general soil profile consists of (from top to bottom), , upper Silty clay horizon (0.0-5.25m thickness) soft to firm for Yenagoa study areas, Medium silty clay horizon (0.75 to 1.5m thickness) soft to firm Yenagoa study areas, low clayey sand horizon (0.75 to 1.5m thickness) soft Yenagoa study areas, peaty clay (1.0m thickness between 3.0-4.0m) soft Igbogene Yenagoa, upper sand horizon (3.0m thickness) silty sand Etegwe town Yenagoa, lower sand horizon (13.5 to 18.0m) silty sand to fine to medium and medium coarse appear in all the boreholes in Yenagoa. Yenagoa sub-soil show clay of high plasticity, silt of intermediate to high plasticity (CH, MI and MH) according to unified soil classification system from the results it shows that pad foundation is more economical in the study areas. Raft foundation is more economical in the six towns study areas of Yenagoa with Allowable bearing capacity of the upper clay layer ranges from 23-128KN/m2 In view of the significant variations in the stratification and engineering geological index properties of the soil in the six towns in Yenagoa while geotechnical data of one location cannot be used as a basis for design of foundation in a nearby land. Axial load carrying capacity for 305, 306mm, 356, 360mm, 406mm, 600and 610mm diameter for bore pile and tubular driven steel cased piles respectively were calculated for all the studies areas. Where high rise building is required in the various study areas. The study shows that the frequent causes of building collapse in Yenagoa are as a result of inadequate geotechnical investigations of the subsoil, poor quality materials, and poor work supervision.

Seabed Observations at the New England Mud Patch: Reflection and Scattering Measurements and Direct Geoacoustic Information

Seabed reflection and scattering measurements were conducted at the New England Mud Patch to better understand the acoustic properties of fine-grained (muddy) sediments. The measurement philosophy and the measurements themselves are summarized. In addition, geoacoustic information accessed directly from the data in the time and frequency domains is presented. The main result is the existence of an angle of intromission. This observation proves that the mud sound speed is less than that of the water and yields a sediment sound speed ratio 0.9865 with outer bounds {0.985 0.989}. Another result is the observation of strong scattered arrivals from within the mud volume at/near normal incidence but not at low grazing angles. These are likely due to anisotropic sediment heterogeneities with a large horizontal to vertical scale. Evidence is also presented for a highly heterogeneous mud–sand horizon with lateral variability down to scales of order meters. Finally, the reflection measurements successfully capture Bragg interference patterns. Their importance is their substantial geoacoustic information content, which can be accessed by several inversion methods.

Geological footprints of the 1945 Makran tsunami from the west coast of India

27th Nov 1945, witnessed a Mw ~ 7.8 earthquake which triggered a tsunami in the coastlines of the northern Arabian sea. The 1945 Makran tsunami caused tremendous loss to the coastal communities of Iran, Pakistan, Oman and India. Despite the recent thrust in tsunami research along the western coast of India, the geological signatures of the 1945 Makran tsunami remained elusive. Here we present the first geological evidence of this event inform of a sand-sheet archived in the palaeomudflats of northwestern Saurashtra coast, western India. Based on the optical simulated luminiscence ages and available storm record of the Arabian Sea, the sand horizon seems to be linked with the 1945 Makran tsunami. The documented sand-sheet shows physical, geochemical and biological characteristics such as basal erosional/sharp contact with the underlying unit and lack of sorting along with the presence of mud-clasts. The sedimentary layer also shows an abnormal inland extent of >570 m from the present high-water line. The sedimentary character of the deposit would serve as a templet at other similar activities in the region as well as will contribute to the overall coastal hazard assessment in the rapidly developing region.

DEM investigation of sand response during displacement pile installation

Previous experimental and numerical studies indicate that the stress state of sand at a specific depth changes significantly during the installation of a displacement pile. At a given depth level, the horizontal stress in sand increases as the end of pile approaches and reduces as the pile continues to penetrate and go past the sand element. This horizontal stress reversal, together with the large-strain deformation of the sand at the pile shaft, may cause a reduced accuracy in the calculation of pile capacity. In this paper, the micro-mechanical behaviour of sand developed around pile shaft during the installation of a closed-ended pile was studied using the two-dimensional Discrete Element Method (DEM). Sand assembly was modelled as uncrushable discs, and the closed-ended pile was modelled as a rigid clump which was made of a large number of overlapped discs with a fixed distance. The sand responses in terms of stress, strain and volume changes during the monotonic jacking of the closed-ended pile were investigated. Simulation results revealed micro-mechanical behaviours of the sand in both the interface zone “B” adjacent to the pile shaft and the far field zone “A” away from the pile. It was shown that the sand along the pile shaft at a small normalised distance to pile tip was subjected to a volume reduction as the pile goes past. As the pile drives deeper, the sand at a larger normalised distance to pile tip exhibited dilation. This captured process will give insights to the degradation of shaft friction at a given sand horizon.

Fossil fish otoliths from the Chibanian Miyata Formation, Kanagawa Prefecture, Japan, with comments on the paleoenvironment

The Paleo-Tokyo Bay (Kanto Plateau) that persisted during the transgression periods in the Middle-Late Pleistocene is known for its rich marine fauna that accommodated both the warm and cold water taxa brought by the Kuroshio and Oyashio Currents, respectively. However, little is known on the paleoichthyofauna in this area and the processes shaping the marine ichthyofauna of modern southern Kanto. We used fossil fish otoliths and teeth discovered in the Sha’ana Tuffaceous Sand Member belonging to the Chibanian Miyata Formation, exposed at Sha’ana-dai, Miura City, Kanagawa Prefecture, Japan, to reconstruct the paleoichthyofauna and its associated paleoenvironment and explore the content of fish assemblages during this period. The Sha’ana Tuffaceous Sand Member was composed of upper sandy mud and lower muddy sand horizons at the exposure. A total of 1,675 fish remains were collected from this site, of which 1,389 were assigned to 62 distinct taxa (20 orders, 31 families). The taxonomic composition revealed taxa from various environments, including shallow continental shelf, epi- to meso-pelagic settings, and the majority were from a generally temperate climatic zone. Paleoenvironmental analyses suggested that the fish assemblages were from the continental shelf (approximate depth of 100–200 m) in a temperate sea where both warm Kuroshio and cold Oyashio Currents had an influence on the biota. The analysis also showed that two boreal fishes, namely Clupea pallasii and Theragra chalcogramma, once had a wider distribution that extended to the southwestern areas of the Paleo-Tokyo Bay. This study provides a more complete view of the related paleobiogeography of marine fishes during the Chibanian and is essential for reconstructing the evolutionary processes of the rich ichthyofauna in the southern Kanto.

Геологічна будова і перспективи нафтогазоносності ділянки Погар (Складчасті Карпати)

The Pohar plot is situated in the Skole district of the Lviv Region, 30 km south-west of Skole town, between Pohar and Kryve villages. Tectonically it is located in of junction of the Skybian (Slavske Skyba) and the Krosno covers. At the end of XIX beginning of XX centuries in the region of the village the oil-extracting enterprise was existent. There deposits of Oligocen and Eocene of the Rozluch belt of the Krosno cover and Oligocene of the scale of the Slavske skyba of the Skybian cover were exploited. During two ten-years of exploitation by exploring shafts and shallow boreholes more than 3 thousand ton of oil was extracted. Prospects of the Pohar plot should be connected with sand horizons of the Holovets suite of Oligocen (Klivsky sandstones) that are characterized by satisfactory reservoir properties. They are localized in the immersed part of the Hrosivsky scale of the Krosno cover separated by the Rozluch fault (tectonically screened deposit) from its forkball part, drilled in 1973–1974 1-Pohar borehole (well bottom 1935 m), due to deflection of its hole to the south-east, didn’t expose the Klivsky sandstones and didn’t solve its task. For complete exposition of the Klivsky sandstones of the Holovets suite of Oligocene of the Hrosivsky scale it is necessary to design vertically oriented 2-Pohar borehole of 2300 m in depth. About probable commercial oil-gas saturation of the horizon of the Klivsky sandstones testifies not only to the existence of the oil-extracting enterprise in the past, but the intensive surface oil shows in the stretched area that is controlled by the Rozluch fault. Moreover, taking the prospect of the zone of junction of the given covers in consideration, the seismic survey should be conducted at the Pohar area for the estimation of the geological structure of the deeper horizons and parametric borehole of 4000–5000 m in depth should be designed.

Seasonal Comparison of Potential Groundwater Aquifer in Ijebu-Ife, South-West, Nigeria, using Dipole-Dipole Array and Electromagnetic Methods

Seasonal comparison of potential groundwater aquifer unit using integrated geophysical methods at Ijebu-Ife, Ogun State, South-west, Nigeria was investigated. The fieldwork employed two seasons (dry and wet seasons). The electromagnetic method employed the Very low frequency and its data was acquired during the dry and wet seasons along with five profiles of Dipole-dipole array covering 500 m length using ABEM WADI VLF equipment and was processed using the KAROUS-HJELT software. The 2 – D Dipole-dipole data were also acquired along with five (5) traverse for both seasons making a total number of ten (10) and was processed with DIPROFWIN software. The results of the Integrated Dipole-Dipole and VLF-EM data identified three geoelectric layers based on its electrical resistivity and conductivity distribution. The study identified a clayey sand horizon which constitutes a good aquifer zone. The study reveals in, comparison, that during the dry season, all layer resistivities are high with low depth while during the wet season; all layer resistivities are low with high depth. Also, conductivity during the wet season is high at high depth than conductivity which is low at low depth during the dry season. The study concluded that, in water exploration, drilling of water should be done during the dry season in other to locate the exact depth of water.
 

Unique Rhenium Deposit in the Carboniferous Coal-bearing Sands of the Russian Plate: Communication 2. Ore Mineralogy

The paper reports geochemical and mineralogical data on ores of the Briketno-Zheltuhinskoe U–Mo–Re deposit, which is confined to the Visean paleochannel coal-bearing sandy sediments of the Moscow lignite basin. In addition to main ore elements (Re, Mo, U, and Se), the ores have elevated contents of the following metals (in order of decreasing abundance): Zr, Zn, Mn, Ni, As, Co, V, Pb, Y, Cu, and highly dispersed Tl and Ag. It was found that Re correlates positively with Mo, Ag, Zn, U, Se, and Co. The ores are incoherent and analytical scanning electron microscopy is the main method applied for their study. In order to clarify the speciation of U, Mo, and Re, sequential extraction experiments were performed. The main part of Re is associated with the organic and ion-exchange forms. Molybdenum is approximately equally distributed between the strongly bound (sulfide) and organic-related forms. Uranium mainly occurs in a weakly bound form and easily migrates with water. Authigenic minerals are mainly represented by pyrite, less common marcasite, and accessory sulfides (sphalerite, chalcopyrite, galena, etc.) and selenides (dzharkenite, clausthalite). Mo-minerals (containing up to 1.5 wt % Re) are represented by the tiny grains of molybdenite and jordisite. Uranium occurs as micron-size inclusions of uraninite (pitchblende) in colloform pyrite and is present as a macro-impurity in rhabdophane and zircon. The predominant part of U, Mo, and Re was found in adsorbed forms in carbonaceous, clayey, and strongly altered sulfide particles. Arkose and subordinate ash material together with heavy metals (Fe, Ni, Cu, Zn, Pb, U, Mo, Re), and also S and Se, were transported by river streams and accumulated in terrigenous sediments of shallow marine basin. These elements were adsorbed by plant detritus and, partly, by clay particles and iron oxyhydroxides/sulfides during diagenesis. The main economic U–Mo–Re ores were formed at the second, epigenetic stage, in the course of the lateral filtration of oxygenated groundwater through highly permeable sand horizons. This process was accompanied by the redeposition of U, Mo, Re, Se, Cu, Ni, and Zn from dispersed mineralization of the first stage at the reducing (plant detritus) and sorption (clay sediments) geochemical barriers. In this case, U, Mo, and Re were fixed in the mineral and, mainly, adsorbed forms. Significant contribution to the ore formation was likely provided by endogenous factors associated with activation of faults in the East European Platform (EEP) basement, epiplatform alkaline-basaltic magmatism, and the influx of deep fluids into the ore deposition zone.

Seismic refraction study, single well test and physical core analysis of anthropogenic degraded Peat at the Badas Peat Dome, Brunei Darussalam

The Badas peat dome located in the Belait district is one of the biggest peat domes in Brunei. Over the years, this area has seen a noticeable loss of peatland due to fires and infrastructure development. In this paper, the anthropogenic effects on the Badas peat dome were studied for three survey areas using seismic refraction surveys, core analysis and single well tests. Satellite images were used to confirm the extent of past peat fires in the area. Using these methods, this study has identified multiple peat, sand and clay layers demonstrating the stratigraphic heterogeneity that can be present in tropical peatlands. In particular, a sand horizon underlying the peat deposits was identified which has the potential to be a significant hydrogeological flow unit. Groundwater level interpretations from 2D velocity data were correlated to groundwater levels from coring. In order to determine the degradation impact on peat through lowering of groundwater levels using these methods we produced a subsurface reconstruction at two locations with different levels of peat degradation. Single well tests conducted in this study showed that disturbed peat had lower hydraulic conductivities with an average of 1.73 × 10−5 m/s compared to undisturbed peat with an average of 6.66 × 10−5 m/s. A combination of these methods (seismic refraction, single well test and coring) are suitable for identifying different levels of peat degradation. In addition, these methods can be suitable for profiling in tropical peatlands, for identifying groundwater levels as wells as identifying significant hydrogeological flow units.

Unique Rhenium Deposit in the Carboniferous Coal-bearing Sands of the Russian Plate: Communication 1. Geological Structure

The Briketno-Zheltukhinskoe U–Mo–Re deposit is located in the southern sector of the Moscow lignite basin (central East European Platform). It is restricted to the paleochannel and deltaic coal-bearing sandy sediments of the Visean Bobrikov horizon lying on the Famennian limestone. They are overlain by the younger Neogene–Quaternary sands and clays. Tectonically, the deposit is ascribed to the southern shoulder of the Pachelma aulacogen crosscut by the SN-trending fault zone. The presence of a thick gray-colored unit of inequigranular moderately and poorly sorted sands containing the coalified plant detritus served as the main lithological-facies factor for the localization of U–Mo–Re mineralization. The Bobrikov sandy formation was accumulated in the fluvial, swampy, onshore deltaic, and shallow-sea lagoonal environments with warm humid climate. A combined syn-epigenetic model is proposed to explain the formation of the U–Mo–Re paleovalley-type deposit. Subeconomic stratabound U (±Mo, Re) mineralization associated with the carbonaceous and clayey horizons was accumulated during sedimentation and diagenesis. During epigenesis, the U–Mo–Re ores were deposited by oxidized groundwater owing to its lateral filtration through highly permeable sand horizons and metal accumulation at the reducing and sorption barriers. The general subhorizontal stratiform structure of the ore deposit is complicated by the subvertical morphological (swell of sand horizon plus strong pyritization) and concentration (Re + Mo column-like maximums) ore shoots. They occur in dome-like structures that disturb the horizontal structure of the host sedimentary unit. It is possible that these domes and ore shoots are the result of hydrothermal-hydraulic processes caused by the activity of deep crustal (likely, mantle as well with allowance for the Re mineralization) fluids.

Preliminary data on formation and depositional environments of lake Chaika in the central part of the Curonian Spit (Kaliningrad region, Russia, South-Eastern Baltic)

Lake Chaika is the only major water body present in the sand barriers of the entire territory of South-Eastern Baltic shoreline. The article provides new insights into the formation of Lake Chaika, based on data acquired through a lithological investigation of the lake sediment core combined with an organic matter content analysis, a macrofossil analysis, a radiocarbon AMS-dating and a bathymetric survey. The study revealed that Lake Chaika was formed around 500 years ago. The kettle of the lake appears to have not been submerged during the Littorina transgressions. During the mid-late Holocene, the kettle of the lake was occupied by the peat-forming ecosystems of alder carrs and sedge fens with scattered alder. The accumulation of ligneous and sedge peat occurred. The sand horizon, separating the gyttja layer from peat deposits, is considered to be a time marker for the so-called “sand disaster”, which began in the study site 200-250 years earlier than in the main territory of the Curonian Spit. There are three main formation phases of the lake’s ecosystem: the period of carrs (5390–510 cal. yr BP), the “sand disaster” period (≈550–500 cal. yr BP) and the proper lake period (500 cal. yr BP – present time).

Runoff processes and lateral transport of soil total carbon induced by water erosion in the hilly region of southern China under rainstorm conditions

Soil erosion by water destroys the physical protection of carbon in soil aggregates and accelerates decomposition, thus impacting soil organic carbon stocks and making the soil barren. Runoff process and lateral transport of soil total carbon were studied using sloping flumes in an artificial rainfall simulator. The flumes were filled with soil collected from the surface horizon, the underlying laterite horizon, and the deeper sand horizon, three portions of a weathered granite soil profile. The results showed that the initial runoff-yielding time was faster under large rainfall intensities and steep slope gradients. The runoff process on sand soil slopes showed a trend of increasing with the increase of rainfall duration, while the trend on surface soil slopes and laterite soil slopes were mainly increasing rapidly and then stable. The volume of overland flow on surface soil slopes was the largest under the same conditions, with an average value of 14,259 mL, while it was the smallest on sand soil slopes. There was no interflow on surface soil slopes, and the interflow curves of the sandy soil slopes and the laterite soil slopes were all single-peak curves. The TC concentration curves of overland flow on sand soil slopes presented a high initial concentration and were then decreasing to a stable state, but the trends on laterite soil slopes and surface soil slopes was not obvious. The TC concentration curves of interflow on sand soil slopes and laterite soil slopes were similar to those of the runoff process curves, and the TC concentration on laterite soil slopes peaked faster. The TC loss gross amount on sand soil slopes and laterite soil slopes was much larger than that on surface soil slopes. Sediment was the main carrier of TC on sandy soil slopes, which TC loss with sediment was more than 50% in each rainfall test. Runoff was the main carrier of TC on laterite soil slopes and surface soil slopes; TC loss with runoff was above 60% on surface soil slopes. At the same time, partial correlation coefficients showed that rainfall intensity was the most important factor affecting TC loss. The results can provide a calculation method and scientific basis for the estimation of the TC loss on weathered granite soil slopes in the south of China.

Coastal dune dynamics along the northern Curonian Spit, Lithuania: toward an integrated database

Sand dunes are the most prominent subjects of geological and geomorphological interest along the Curonian Spit – a mega-barrier that separates the Curonian Lagoon from the Baltic Sea. To date, an assessment of various parameters of migrating dunes along the spit has been based on comparative analysis of old maps or aerial and satellite images, as well as geodetic measurements. These investigations have allowed assessment of dune dynamics over a relatively short historical period (~1700s to present). The most recent detailed investigations of the Dead (Grey) Dunes along the Lithuanian part of the spit using ground-penetrating radar (GPR) and magnetic susceptibility (MS) surveys, supported by a radiocarbon ( 14 C) chronological framework of palaeosols and infrared optically stimulated luminescence (IR-OSL) ages of sand horizons, have advanced our understanding of aeolian landscape evolution. The interpretation of dune activity and stability phases has been generally based on IR-OSL dating results of the sand layers located between radiocarbon-dated palaeosols. However, the influence of soil-forming processes on the IR-OSL dating results related to possible migration of natural radioactive isotopes via aeolian sand layers has not been previously considered. Hypotheses of dune reactivation and migration caused by abrupt regional climate shifts, catastrophic forest fires, anthropogenic influence, and more local forcings have been tested. An integrated approach to dune investigations has offered an estimate of the rates of sand accumulation and key phases of aeolian dynamics during both stormy and calm periods, as well as helped to extend the record of dune evolution to the mid-Holocene. The palaeoenvironmental and palaeodynamic reconstructions of the Dead Dunes suggest that this mid-Holocene phase of dune activity was of a local character and likely did not exceed several centuries.

Integrated Geotechnical and Geophysical Investigation of a Proposed Construction Site at Mowe, Southwestern Nigeria

Abstract The subsurface of a proposed site for building development in Mowe, Nigeria, using Standard Penetration Test (SPT), Cone Penetrometer Test (CPT) and Horizontal Electrical Profiling (HEP), was investigated with the aim of evaluating the suitability of the strata for foundation materials. Four SPT and CPT were conducted using 2.5 tonnes hammer. HEP utilizing Wenner array were performed with inter-electrode spacing of 10 – 60 m along four traverses coincident with each of the SPT and CPT. The HEP data were processed using DIPRO software and textural filtering of the resulting resistivity sections was implemented to enable delineation of hidden layers. Sandy lateritic clay, silty lateritic clay, clay, clayey sand and sand horizons were delineated. The SPT “N” value defined very soft to soft sandy lateritic (<4), stiff silty lateritic clay (7 – 12), very stiff silty clay (12 - 15), clayey sand (15-20) and sand (27 – 37). Sandy lateritic clay (5-40 kg/cm2) and silty lateritic clay (25 - 65 kg/cm2) were defined from the CPT response. Sandy lateritic clay (220-750 Ωm), clay (< 50 Ωm) and sand (415-5359 Ωm) were delineated from the resistivity sections with two thin layers of silty lateritic clay and clayey sand defined in the texturally filtered resistivity sections. Incompetent clayey materials that are unsuitable for the foundation of the proposed structure underlain the study area to a depth of about 18m. Deep foundation involving piling through the incompetent shallow layers to the competent sand at 20 m depth was recommended.

Trap Analysis of “Covenant” Field in Niger Delta, Nigeria

The tendency to identify leaking zones is essential tool in trap assessment. Faults play an important role in creation of hydrocarbon traps. For volumetric analysis of a field to be meaningful, it is essential to analyze the faults contributing to the accumulation of hydrocarbons in a trap. These faults may be sealing or act as conduit to fluid flow. Analysis of trap is therefore carried out with the aim to reduce the uncertainties associated with hydrocarbon exploration and exploitation in Niger-Delta using “Covenant” field as a case study. The aim of the study is achieved using three dimensional seismic and well log data. Three reservoirs were mapped on the field while the fault supporting the identified trap was analyzed via throw, shale volume, shale gouge ratio, and hydrocarbon column heights attributes. The volume of shale model shows the presence of shale and sandstone formations in the fault plane. The fault-horizon’s intersection (throw) model reveals that the horizons were not too deviated from where the maximum fault’s displacement was noticed. The estimated shale gouge ratio of the fault on the analyzed trap reveals that the shallow sand horizon is supported by moderate sealing plane while that of mid and deep sand horizons are supported by proper sealing fault plane. The hydrocarbon column height model reveals a column height of 120m supports the shallow sand horizon while column heights \(> 180\) m support the mid and deep sand horizons respectively. It was inferred that despite the three horizons are supported by sealing fault zone, leakage still occurs at shallow sand horizon which correspond to a moderately sealed plane from SGR.

The revision of Quaternary stratigraphy of the Sombor and Subotica artesian well borehole profiles (Bačka, Vojvodina, Serbia)

The results of stratigraphy of the Sombor and Subotica boreholes were first results of geological examination of borehole material from Vojvodina published by Halaváts in 1895. These geological profiles, alongside the borehole profile in Zrenjanin, were recognized as “standard” profiles for Quaternary geology and stratigraphic correlation pertaining to Vojvodina. However, the results of taxonomical revisions for malacologic material, published in 1977 by Krolopp and which presented significant changes in stratigraphy, have not been implemented in the results of geological mapping/surveying. According to new advances and results regarding Quaternary stratigraphy, Lower Pleistocene sediments can be better defined using Pleistocene Corbicula beds, the Viviparus boeckhi Horizon and the results yielded by this paper.In the case of the Sombor borehole, the Lower Pleistocene was defined at a depth from 48.13 m to 149.5 m, according to its palaeonological record (molluscan assemblage). The Lower- and/or Middle Pleistocene were defined as the interval between a 35.45 m and 48.13 m depth, based on sedimentology (lignite) and malacology. The interval from 15.21 m to 35.45 m depth was identified as Pleistocene, based on superposition and palaeontological material. The yellow quartz sand horizon at 9.74 m–15.21 m remains undefined. The Holocene yellow silty-clay horizon, which ascends to a 9.74 m depth, was identified as Holocene, according to the palaeontological content of the same sediments found in the brickyard in the vicinity of Sombor.In the case of the Subotica borehole, the Lower Pleistocene – based on palaeontological records – was defined at a depth between 99.6 m and 124.5 m. The depth from 2.2 m to 99.6 m could not be exactly identified as Pleistocene, while Holocene quicksand ascended to a 2.2 m depth.

Soil hydrology, physical and chemical properties and the distribution of carbon and mercury in a postglacial lake-plain wetland

Northern wetland soils hold globally significant carbon (C) and mercury (Hg) stocks whose cycling feeds back to atmospheric pollution, climate change, and the trophic dynamics of adjacent aquatic ecosystems. At a more local level, patterns of variation in the hydrologic, physical and chemical properties of wetland soils inform the appreciation of these ecosystems in their own right; describing patterns of variation, their potential drivers and consequences is a key step towards placing wetland soils in the context of broader landscape-level processes, such as C and Hg export to aquatic ecosystems. In this case study, we investigated a 10ha, 3000year old lake-plain wetland in the Great Lakes region (U.S.A.), located at the interface between a 120ha, first-order watershed and a 6700ha inland lake. We monitored water tables, measured soil morphology and physical characteristics, applied interpolation and mapping to model hydrologic flowpaths and spatial variation in soil depth, morphology, total C and Hg stocks, and used chemical analyses (elemental concentrations and isotope signatures, UV–Vis and FTIR spectroscopy) to quantify relationships between soil C and Hg pools, organic matter composition, and C cycling rates. Key findings from this site include: 1) whole-profile soil C and Hg stocks are readily predicted from soil depth; 2) soil saturation is semipermanent but spatially and temporally variable; 3) accumulated organic soil materials are dominated by aromatic moieties, but possess considerable amounts of labile polysaccharides; 4) subtle, topography- mediated hydrologic flowpaths create profiles of interbedded organic and mucky sand horizons with sharp discontinuities in their C and Hg concentrations. Compared to peatlands across the region and North America, soil depths and C stocks are rather low, averaging 84cm and 394Mgha−1, respectively. On the contrary, total Hg concentrations of organic soil materials (137 and 191ngg−1 for fibric vs. sapric, respectively) are at the high end for wetlands of the Great Lakes region, and more representative of those observed in areas of the eastern U.S. with historically elevated atmospheric deposition. Given past and potentially increased future variation in hydrologic regimes due to climate change, the presence of banded (sandy) profiles that may act as preferential flowpaths, and the large quantities of Hg and labile C held in these soils, they may act as significant sources of C and Hg to the atmosphere or adjacent aquatic ecosystems.